In order to provide real time communication of audio, video and data signals between a moving vehicle and a fixed ground station, the vehicle may be provided with an antenna for beaming a signal to a helicopter located above the car. The helicopter then relays the signal from the car to and from a fixed ground station. This system of communicating data between a moving vehicle and a fixed ground station has been particularly useful in the field of motor racing to provide video, audio and data signals from the cars and to allow data and audio signals to be transmitted back to the car.
Current on-board cameras use a microwave transmitter system for communication up to the helicopter. The helicopter then re-transmits a signal on a second microwave frequency to the fixed location.
There are a number of drawbacks associated with such a system. If a car that is providing the signal does not have a direct line of sight to the helicopter, for example because of tall trees or buildings at the side of the track, then the received signal may be weak or obscured completely. In such a situation, it is necessary for the helicopter to remain almost directly above the vehicle to maintain a consistent contact with the car. This can be difficult, particularly with high-speed racing such as Formula One where the helicopter is unable to match the speed of the cars it is attempting to follow. Alternatively, the helicopter can fly at a greater height to avoid objects coming between it and the car. However, this again can reduce the signal quality received by the helicopter due to the increased distance. This can also lead to problems with air traffic control. A further problem of using a helicopter to relay signals is its dependence upon the weather. If the weather becomes unsuitable for flight then it is not possible to provide the signal relaying function at all.
A further limitation of the use of helicopters for relaying signals is the limited amount of weight that can be carried to allow the helicopter to remain at its station for the duration of a race. Similarly, there is a limitation on the amount of power that can be provided for running the radio frequency systems.